Muffler



C. C. MOSS Sept. 4, 1956 MUFFLER 5 Sheets-Sheet 1 Filed July 26, 1950\www 6/7? c? Ma s.

C. C. MOSS Sept. 4, 1956 MUFFLER 3 Sheets-Sheet 2 Filed July 26. 1950.

INVENTOR. CZQSZW CT /Vassz BY W 0175M Sept. 4, 1956 Filed July 26, 1950C. C. MOSS MUFFLER 3 Sheets-Sheet 3 INVENTOR. 6%esfer C Mass,

United States Patent MUFFLER Chester C. Moss, Jackson, Micl1., assignorto Walker Manufacturing Company of Wisconsin, Jackson, Mich., acorporation of Wisconsin Application July 26, 1950, Serial No. 176,017

13 Claims. (Cl. 181-62) This invention relates generally to muffiers forthe prevention of noise caused by pulsating gases and, in particular, tothe housings or shells of such devices.

Although the invention is useful in devices for mufiiing pulsating gasesgenerally, e. g., muffiers for the intake and delivery of aircompressors, the most severe requirements are met in the prevention ofnoise caused by the exhaust of internal combustion engines, andespecially engines for automobiles or other units that are intended forproduction on a large scale at a low cost. For this reason, theinvention will be illustrated and described herein as applied toautomobile mufflers.

It is the object of this invention to reduce shell noise in mufliersand/or to reduce the escape of heat through a selected area of themuffler shell.

In order to accomplish this object, the invention provides a new type ofouter shell for mufflers. This shell may be used with substantially alltypes of internal apparatus for eliminating the noise of pulsatinggases. It is of the double wrap type, i, e., a double layer shell formedfrom a single continuous sheet of flat metal, and has a layer ofasbestos or similar sound deadening or insulating material between themetal layers. The asbestos layer substantially eliminates shell noisedue to sympathetic vibration of the shell wall and also reduces theescape of heat through the shell, a feature of importance in some of thelate model automobiles.

Layers of asbestos or the like have been applied to muffier shellsbefore. The present shell, however, gives entirely satisfactoryperformance in all respects and, at the same time, is substantially lessexpensive to manufacture than the prior lined shells since it is simplerto assemble and requires less metal. In fact, the shell of thisinvention is inherently stronger than the prior lined shells and isblowout proof and leakproof.

The features of this invention will become more apparent uponconsideration of the accompanying drawings, in which:

Figure l is an axial section through a muffler having a shellconstructed in accordance with the principles of this invention;

Fig. 2 is an enlarged cross-section of the mufiler take along the line2-2 of Fig. l; i

Fig. 3 is a reduced plan view of the blank from which the mufiler shellis formed;

Figs. 4 and 5 are side elevationals of rolling apparatus that may beused to form the shell from the blank of Fig, 3;

Fig. 6 is an axial section through a different type of muflier whereintransverse partitions are Welded to the shell;

Fig. 7 is a reduced end view taken from the left of Fig. 6;

Fig. 8 is an enlargement of the structure shown in a section along line8-8 of Fig. 6 and shows the embossment formed on the shell to facilitatewelding of the partitions thereto;

Fig. 9 is a reduced plan view of the blank that may be used to form theshell of Fig. 6;

Figs. 10 and 11 are sections taken along the line 1t)-10 of Fig. 9 andshow two modified forms of blank, the blank of Fig. 10 having metalwhich is ordinarily flat so that embossing takes place in weldingoperation while the blank of Fig. 11 has the embossment already formedin the metal;

Fig. 12 is a section through another type of mufiier whereinlongitudinal partitions are welded to the shell lengthwise thereof; and

Fig. 13 is a plan view or" a reduced blank that may be used to form theshell of Fig. 12.

"Referring first to Figs. l-5, a cylindrical mufiler 1 is illustratedwhich has an outer shell 3 and internal sound eliminating apparatus 5.The apparatus 5 has longitudinally spaced transverse partitions (ormounting members) 7 that are slidably mounted within the shell 3. It isalso mounted upon transverse covers or headers 9 that are fixedlysecured to the opposite ends of the shell 3.

While, generically, the internal apparatus 5 forms no part of thepresent invention and may be of any desired type, as will hereinafterbecome more evident, it may be noted that in the muffler 1 it includestwo concentric tubes 10 and 11 located within the shell 3. The two tubesform an annular tuning neck 12 and the outer tube forms with the innersurface of the shell 3 a resonating chamber 13. The innermost tube It)is mounted in the surrounding tube 11 by means of transverse partitions15 which divide the annular space between these tubes into a series ofspit chambers 17 that are extensions of the tuning neck 12. Thepartitions 7 form a series of silencing chambers 19 for intermediatefrequencies which are extensions of the resonating chamber 13.

As best revealed in Fig. 2, the shell 3 is formed from a single sheet ofmetal that is wound about the axis of the muffler twice so as to form awall consisting of an inner layer 21 and an outer layer 23. The oppositeside edges of the metal which form the shell 3 are overlapped to form ajoint 25 and the three thicknesses of metal are spot welded at spaced,longitudinal intervals along this joint, the spot weld being indicatedby the numeral 27. Between the inner and outer layers 21 and 23 is asheet of asbestos 29 or other material which is effective in insulatingagainst sound caused by vibration of the walls 21 and 23 and which, inaddition to, or instead of, may insulate the walls 21 and 23 against thepassage therethrough of heat dissipated in the mutlier. Materials forthis purpose are well known in the art and commercially available.However, as indicated, asbestos is, at the present time, preferred.

The shell 3 thus is basically what is referred to as a double wrappedshell which has added the insulating sheet 29 thereto between the layersof metal. While the shell may be formed by separately coiling the sheetsof metal and asbestos and then inserting asbestos coil between the twolayers of the metal coil, it is preferably formed by the methodindicated in Figs. 3-5. The shell originates from a flat piece of sheetmetal 31 which has its opposite ends 33 spaced apart by the requiredlength of the shelland its side edges 35 spaced apart by a distanceequal to substantially twice the circumference at the mean diameter ofthe shell wall plus the width of the joint 25. The sheet of asbestos orother material 29 is laid on the blank 31 and may be attached thereto byglue, cement, or other convenient means, if desired. The sheet 29 has alength which is a little less than that of the shell 3 and it is placedon the blank so that its ends 37 are spaced inwardly from the ends 33 ofthe blank, this being done for a purpose which will hereinafter becomeapparent. The width of the sheet 29 is substantially equal to thecircumference of the shell 3 along a mean diameter less the width of thejoint 25. The sheet 29 is placed on the blank 31 so that one of its sideedges 39 is spaced inwardly from a side edge 35 of the blank 31 by adistance which is substantially equal to the width of the joint 25.

The flat blank 31 with the sheet 29 attached is then fed into theforming rolls 41 shown in Figs. 4 and 5. A side 35 of the blank 31 whichis remote from the sheet 29 is preferably fed into the rolls 41 first sothat the sheet 29 is adjacent the trailing edge as indicated in Fig. 4.It is evident from the drawings that the blank will be rolled up so thatthe forward half of the blank forms the inner layer 21 and the trailinghalf forms the outer layer 23 with the sheet of asbestos 29 in between.The overlapping side edges 35 of the blank 31 are then pressed againstopposite sides of the intermediate layer of metal and spot welded in asuitable jig and in accordance with conventional practice, it beingnoted that the sheet of asbestos 29 has been located so that it does notlie in the joint 25.

After the shell 3 has been formed in the manner just indicated, theinternal apparatus 5 may be slid in place on the inner layer 21. Theheaders 9 may then be slid onto the tube 10 and secured to the ends ofthe shell 3 in a joint 43. For the sake of economy and strength, thejoint 43 is preferably formed by reverse bending the ends of the shelland the outer periphery of the headers so that they are interlocked asclearly shown in Fig. 1. Either during this operation or prior thereto,the ends of the layers 21 and 23 of the shell 3 are brought into contactby bending the end of the outer layer 23 against the surface of theinner layer 23, this being permitted by virtue of the spacing of theasbestos sheet 29 from the ends 33 of the shell blank 31.

The mufiler 51 of Figs. 68 is oval rather than circular in cross-sectionand thus has an oval shell 53. The ovalshaped shell may be producedconveniently by flattening the opposite sides of a cylindrical shellformed on the rolls 41 of Figs. 4 and 5. The muffler 51 has an internalnoise eliminating apparatus 55 which includes transverse partitions 57that are spot Welded at 59 to the shell 53. In order to permit spotwelding by passage of electric current through the entire thickness ofthe shell 53, the abbestos layer 61 between the inner and outer layers63 and 65 of the shell is adapted by means shown in Fig. 9 (or indicatedin Fig. 13) to provide suitable apertures that enable metal-to-rnetalcontact among the shell layers 63, 65, and the partition 57. Thus, theshell 53 may be formed from the blank 71 having the layer 61 placedthereon as indicated in Figs. 911. The sheet 61 is located on the blankof shell metal 71 in the same manner as described in connection withFigs. 35. The sheet 61 has apertures 69 of a suitable type formedtherein to enable welding of both shell layers to the partition, andhence, these are spaced from the ends of the sheet 61 and from the endsof the blank 71 so as to lie in the planes of the partitions 57. Theblank 71 may be entirely flat as shown in Fig. 10, and the outer layer65 pressed against the inner layer 63 during the spot welding operation.Alternatively, as in Fig. 11, the blank 71 may be provided withembossments 73 of a depth that is substantially the same as thethickness of the sheet 61 so that they may extend through the apertures69 and contact the inner layer 63 without the application of pressureduring the spot welding operation, though it may be observed that thethickness of the shell metal is light enough so that no substantialproblem is encountered in embossing it during the spot weldingoperation. When the embossments 73 are formed in the blank 71, theseserve to locate the sheet 61 and, to this extent, facilitate themanufacture of the shell.

Figs. 12 and 13 illustrate a muffler 81 having a shell 83 to whichlongitudinally extending partitions 85 are spot welded along theirlength in joints 87. The shell 83 is preferably formed from a blank 89by the method of Figs. 3-5. A single sheet of asbestos 91 may be usedand provided with apertures for the spot welds in the manner indicatedin Figs. 611 or, alternatively, more than one sheet of asbestos may beused as indicated in Fig. 13, it now being evident that the insulationlayer of Figs. 6-11 could also be in the form of spaced sheets to permitspot welding. In the shell 83, the layer does not extend. all around itscircumference but only in two of the three sections defined by the threelongitudinal partitions and thus illustrates that, within the purview ofthe present invention, the insulating layer may be applied to a selectedarea of the shell which is less than its entire area. Since two sectionsare provided with insulation, two sheets 91 may conveniently be employedin the manufacture of the shell. The length of these sheets and theirlocation with respect to the ends of the blank 89 and the sides of theblank are determined in the manner set forth in Figs. 3-5. The blanks 91have a width which corresponds to the circumferential distance betweenadjacent joints 87 and the two sheets are spaced apart by the width of ajoint 87 so that the outer layer of shell metal may be embossed ordeformed inwardly into contact with the inner layer before or during thespot welding operation. The blank 89 with the sheets of insulatingmaterial 91 mounted thereon is formed into the shell by suitable meansthat have been already described.

It will now be observed that the invention provides for the very simpleassembly of an insulating layer between two layers of shell metal. Theshell is united in only a single joint and this consists of three layersof metal that are securely attached by a spot welding operation so thatthe shell is blow-out proof as well as leakproof. Transverse partitionsmay be readily welded to the shell by providing openings in theinsulating layer. The insulating layer may function to deaden noise dueto vibration of the metal shell layers or to prevent escape of heat fromthe mufiler toward the underside of the automobile body. or theinsulating layer may do both. Also, as indicated, the insulating layerneed not be used throughout the entire area of the shell, and in somecases, particularly where only heat insulation is desired, it may be thebetter practice to place the insulation only on the top side of theshell.

What is claimed is:

1. In an exhaust mufiler having an inlet and an outlet for gas, thecombination of a single sheet of metal spirally wound upon itself toprovide a shell having a wall in cluding at least two layers of saidsheet, the sides of said sheet overlapping to form a joint of at leastthree layers of said sheet each in contact with another layer,insulation sheeting in said wall between said two layers, soundsilencing and gas conduit structure connected to said inlet and outletand including a metal mounting member inside of said shell having alayer in engagement with the inner layer thereof to form a joint, saidsheeting being apertured on a radius through said joint to permitmetalto-metal contact between the two layers of said wall, and spotwelds along both said joints interconnecting the metal layers.

2. The invention of claim 1 wherein said sheeting comprises a singlesheet having openings therein to provide the apertures for spot Welding.

3. The invention of claim 1 wherein said sheeting comprises a pluralityof sheets spaced from each other to provide the apertures for spotwelding.

4. The invention of claim 1 wherein said mounting members extendtransversely of the axis of the shell.

5. The invention of claim 1 wherein said mounting members extendlongitudinally of the axis of the shell.

6. In an exhaust muflier having an inlet and an outlet for gas, thecombination of a shell having a wall including at least two layers ofsheet metal, a portion of the side of one of said overlapping layersengaging the other and also its own layer to form a joint of at leastthree layers of said metal each of which is in contact with another,insulation sheeting between said two layers, sound silencing and gasconduit structure connected to said inlet and outlet and including ametal mounting member inside of said shell having a layer in engagementwith the inner layer thereof to form a joint, said sheeting beingapertured on a radius through said joint, an embossment on the outerlayer of said shell extending through the sheeting aperture to contactthe inner layer, and spot welds along both said joints interconnectingthe metal layers.

7. In an exhaust mufller, the combination of a single sheet of metalspirally wound upon itself to provide a shell having a wall including atleast two layers of said sheet, the sides of said sheet overlapping toform a joint of at least three layers of said sheet each of which is incontact with another layer, spot welds uniting said three layers,insulation sheeting in said Wall between said two layers and spaced fromthe ends of the shell, and headers mounted on the ends of the shell andhaving an interlocked engagement with the ends of the shells beyond thesheeting, the layers of shell metal beyond the sheeting being in contactwith each other lengthwise of the shell and in said interlockedengagement.

8. In an exhaust mufiier having an inlet and an outlet for gas, atubular shell comprising two radially spaced layers of metal, at leastone of said layers being overlapped so as to have a portion defined bytwo contacting thicknesses of metal, said portion contacting the otherof said layers so as to form a joint between the two layers including atleast three thicknesses of metal each of which is in contact withanother thickness of metal in the joint, a weld in said joint firmlyuniting together all three thicknesses of metal, a layer of insulativematerial in the radial space between said layers but not in said joint,sound silencing and gas conduit structure connected to said inlet andoutlet and including a metal member within said shell and having aflange in contact with the inner of said metal layers, said insulativelayer having an opening in radial alignment with the area of contact ofsaid flange and inner layer, the outer of said metal layers having aradial embossment extending into said opening and in contact with theinner layer to form with said inner layer and said flange a jointincluding at least three thick- 40 nesses of metal each of which is incontact with another thickness of metal in the joint, and a weld in saidlastmentioned joint firmly uniting together all three thicknesses ofmetal.

9. The invention set forth in claim 8 wherein said member extendstransversely of the axis of said shell and said opening comprises acutout in a sheet of insulative material.

10. The invention set forth in claim 8 wherein said member extendsaxially of the shell and said opening is provided by a spacing betweenthe ends of adjacent sheets of insulative material that constitute saidinsulative layer.

11. In an exhaust muffler having an inlet and an outlet for gas, soundsilencing and gas conduit structure connected to said inlet and outlet,a shell enclosing said structure and comprising a sheet of metalspirally wrapped upon itself to provide a shell wall having two layersof metal, the ends of said sheet being overlapped and secured togetherin a joint having at least three thicknesses of metal, said sheet havingembossments therein acting to radially space apart said two layers, andinsulative material in the radial space between said two layers withaperture means therein through which said embossments extend.

12. In an exhaust mufiler, an elongated shell comprising a sheet ofmetal spirally Wrapped upon itself to provide a. shell wall having twolayers of metal, the ends of said sheet being overlapped in a jointhaving at least three thicknesses of metal, spot welds in said jointsecuring said three thicknesses of metal together, said sheet havingembossments therein in only one of the layers acting to radially spaceapart said two layers, the end portions of the layers of metal atopposite ends of said shell being in contact, end headers at oppositeends of said shell and closing the ends thereof and having a reverselybent interlocked engagement with said end portions, each of said headershaving an opening therein to provide an inlet and outlet respectivelyfor gas passing through the shell, and sound silencing and gas conduitstructure mounted within the shell and supported on the inner peripherythereof and including tube portions mounted in said inlet and outlet ofsaid headers.

13. The invention set forth in claim 12 wherein said sound silencing andgas conduit structure includes a partition aligned with at least one ofsaid embossments and rigidly secured by a spot Weld in said embossmentto said two layers of metal.

References Cited in the file of this patent UNITED STATES PATENTS937,665 Walton Oct. 19, 1909 979,460 Fulton Dec. 27, 1910 1,368,490Dieckmann Feb. 15, 1921 1,618,611 Trout Feb. 22, 1927 1,752,038 SundayMar. 25, 1930 2,014,983 Quarnstrom Sept. 17, 1935 2,113,828 Compo Apr.12, 1938 2,241,768 Deremer May 13, 1941 2,277,132 Moss Mar. 24, 19422,331,325 Jensen Oct. 12, 1943 2,331,344 Powers Oct. 12, 1943 2,634,759Twickler Apr. 4, 1953 FOREIGN PATENTS 435,423 Great Britain Sept. 20,1935 562,192 Great Britain June 21, 1944

